Photosynthetic electron transport associated with oxygen evolution in green plants is being investigated by kinetic applications of electron spin resonance and optical flash spectroscopy. The overall objective of the proposed research include: a. Characterization of the chemical reactants involved in the primary transformation of solar energy into oxidative potential for water splitting. b. Elucidation of the intermediates associated with the manganese-protein complex catalysis of water oxidation. The scientific methodology to be applied in this project includes spectroscopic techniques, oxygen evolution and phosphorylation determinations. Electron spin resonance spectroscopy in conjunction with laster flash-photolysis allows isolation of the paramagnetic transients associated with membrane-linked electron transport.